INSIGHTS Who Selects Fireproofing? By Charles “Chuck” F. King, P.E., S.E., and Stephen M. Cohen, AIA
F
ire is the most common devastating event a building can experience. The structural integrity of a building is vulnerable to high temperatures from a fire because steel melts, wood burns, and concrete cracks! Yet, these are the materials structural engineers use to hold up the building. The materials must maintain integrity during a fire long enough to protect the building occupants and allow firefighters to put out the fire. Building codes provide guidance on protecting buildings and occupants from the effects of fire. Architects and engineers apply the code provisions to contain a fire so all occupants survive and safely escape the premises. The codes specify how long a building must resist fire to achieve this goal. So, who drives the decision for the type of fireproofing used to protect the building elements? Both the architect It is a collaboration between knowledgeable and the engineer have a responsibility to provide these solutions. The structure must be protected, and occupants structural engineers and architects to consider the allowed to escape. So, each professional plays a part in tradeoffs inherent to different approaches. specifying the fireproofing in accordance with the code. When the owner identifies the use of the building and the occupancy load, the architect references the fire codes to classify the building and identify where fire containments (separations) are located. The architect plans the egress avoids the need for sprayed-on fire protection to the underside of the routes (stairs, doors, windows, etc.), applying the fire-resistance rating slab. Of course, exposed beams need to be protected, but eliminating for the walls, ceilings, and floor assemblies. The types of assemblies the need for fire protecting the slab greatly reduces cost. The impact are selected and checked against research from fire prevention labora- of this decision is a slight reduction in the floor-to-ceiling height, tory studies such as Underwriters Laboratory (UL). These reference possibly affecting the architectural design. standards provide precise details for achieving fire ratings for walls, Residential buildings are often constructed with reinforced concrete. floors, etc., that are required to comply with fire codes and, when This material provides built-in fire separation, as concrete has excelapplied, must be constructed precisely as shown. The fire ratings are lent fire resistance, eliminating the need for additional applications or based on lab tests conducted on the various assemblies to assess how assemblies. But the flexibility of the structure for future modifications quickly temperatures reach unacceptable levels. is reduced. It is more difficult to cut a hole in a reinforced concrete In some cases, precise assemblies are not practical for various reasons structure than a steel or wood structure. and, still, the building element must be protected per the code. Faced Numerous options are available for protecting structures; each one with this task, the architect and engineer must now collaborate in has advantages and disadvantages. The priorities of the owner drive preparing, reviewing, and approving fire protection details. the choices. What is the dominant function of the building? Who uses For instance, a popular theme in modern office interiors is an industrial it? What is the expected life cycle? These are questions that should look with an exposed structure. The columns and beams supporting the be answered for all elements of a building design process. And, fire building have an aesthetic appeal desired by the architect. These support protection is a significant consideration when decisions are reached. members must be protected without compromising the aesthetics. A Who should specify? It is a collaboration between knowledgeable popular alternative to sprayed-on cementitious fireproofing, in this case, architects and structural engineers to consider the tradeoffs inheris to employ intumescent paint or mastic coatings that are much thinner ent to different approaches. Sometimes a compromise but, in the and allow the structural elements to be expressed. These coatings have end, protection of life and property drives the final decision. The been developed to swell when heated to protect the structure. They wisdom of these decisions is not apparent immediately but instead protect the steel while satisfying the fire rating requirement. years down the road. If a fire occurs, the owner, residents, and the Sometimes the application of fireproofing impacts the gross square public will be relieved that their building protected the footage calculation the developer wants to maximize. For example, occupants and preserved the property so firefighters could enclosing the columns with a fire-rated assembly reduces the square safely extinguish any fire.■ footage and reduces the rental fee the developer can request from the Charles “Chuck” F. King is Vice President with Urban Engineers of New tenants. With a multi-story building, the reduction in rentable space can York, D.P.C., and the Office Manager of the New York City office. have a substantial negative impact on the cost-benefit to the investors. (cfking@urbanengineers.com) Floor-to-ceiling heights can be affected by the choice of floor fire Stephen M. Cohen is a Managing Director of United Building Sciences, protection. The structural engineer may choose to increase the slab LLC, in New York City. (scohen@ubslny.com) thickness to achieve a fire rating dictated by the code. This approach
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